Vacuum cleaners can be grouped into two basic categories. Vacuum cleaners in the first category use a bag for the filtration and retention of particulate matter. The vacuum cleaners in the second category are bagless and utilize cyclonic separation to remove particulate matter from the vacuum airflow.
One example of a cyclonic vacuum cleaner is the apparatus disclosed in U.S. Pat. No. 739,263. That device has a cylindrical body which is separated by a dividing flange into an upper portion and a lower portion. The upper portion of the cylinder has an outlet port extending through the cylinder wall and the lower portion has an inlet port extending through the cylinder wall. Attached to the dividing flange is a baffle which has a cylindrical hollow body that tapers to a smaller opening at its lower end. The inlet port is placed in the cylinder wall so that air flowing into the cylinder strikes the baffle tangentially.
In operation, air flowing into the cylinder through the inlet port swirls around the baffle and downwardly below the opening in the baffle. The dirt suspended in the air then falls to the bottom of the cylinder and the clean air rises through the baffle interior and into the upper portion of the cylinder. The air then flows through the outlet port towards an externally located pump. An opening is provided in the bottom wall of the cylinder through which the collected dirt is removed.
A vacuum cleaner of the foregoing construction possesses several limitations. First, these vacuum cleaners rely upon gravity alone to remove dirt from the air. If the particles in the air flow are small enough the energy imparted to them from the moving air flow is sufficient to overcome the gravitational pull against the particles and they will remain in the air flow. To overcome this limitation devices incorporating secondary filters which filter the rising air within a cyclonic vacuum cleaner have been built. Devices which utilize such secondary filters are shown in U.S. Pat. Nos. 3,320,727; 3,543,325 and 1,170,438.
The use of secondary filters within such devices have caused additional problems. In devices such as that shown in U.S. Pat. No. 3,543,325, removal of the collected dirt can be quite messy. When the portion of the vacuum cleaner which contains the secondary filter is separated from the body of the vacuum cleaner, the dirt resting against the secondary filter is disturbed during this procedure. This dirt is then dispersed in the immediate vicinity, which is usually in the operator's face. This problem arises because the filtered dirt and the dirt removed by the gravitational pull are collected in two different locations within the vacuum cleaner. This problem is also apparent in U.S. Pat. No. 3,320,727 where a bag filter is used in conjunction with the cyclonic separation method.
Another limitation of some of the known cyclonic vacuum cleaners is the requirement that a second receptacle is necessary to remove the accumulated dirt through the lower opening as shown in U.S. Pat. No. 739,263. A method for eliminating the need for this second receptacle is demonstrated in U.S. Pat. Nos. 3,320,727; 3,543,325 and 1,170,488. All of these patents describe devices which use a receptacle that lies entirely below the cyclonic baffle. These designs still suffer from the limitation that the filtered dirt is not stored in the same receptacle as the dirt separated by the cyclonic separation.